1. Field of the Invention
The present invention relates generally to a semiconductor manufacturing apparatus for forming a thin layer, and more particularly to a chemical vapor deposition apparatus.
2. Description of the Related Art
Metal organic chemical vapor deposition (MOCVD) is a technique for depositing a thin layer onto a substrate by reacting, for example, a group-III gas and a group-V gas with the substrate in a heated reactor. Using MOCVD, it is possible to build up many thin layers with the ability to precisely control the thickness or chemical composition of each thin layer. As such MOCVD is widely used in semiconductor manufacturing processes.
After forming a thin layer in a processing chamber of a reactor, the residual gas in the processing chamber is discharged out of the processing chamber. When the atmosphere temperature drops below the evaporation temperature of the residual gas being discharged, this could induce formation of undesired particles in the processing chamber. The undesired particles may drop onto the substrate in the processing chamber, and it would create difficulties in acquiring the thin layer having a uniform layer quality or a uniform layer thickness distribution. Also, these undesired particles could attach onto a gas discharge path, causing the warm-keeping effect. This warm-keeping effect refers to the temperature difference created between the preset and the actual temperatures of the processing chamber, and this temperature difference will negatively influence the quality of the thin layer.
Furthermore, when uniform flow distribution of processing gas is not achieved, for example, due to a vortex generated in the gas discharge path, even more undesirable particles may be generated. One reason behind the causes of vortex generation is the improper width of the gas discharge path between the susceptor and the nearby wall of the processing chamber.
In a conventional MOCVD apparatus, the width of the gas discharge path between the susceptor and the wall of the processing chamber is fixed by design such that it would not be possible to control the width of the gas discharging path. Therefore, when the fluid flow distribution of the processing gas in the chamber is not proper, it may become necessary that the apparatus be again designed and manufactured.